Server returned HTTP response code: 500 for URL

[Sasuccio87]

Ciao a tutti, qualcuno saprebbe aiutarmi riguardo questa eccezione?

Server returned HTTP response code: 500 for URL:

java.io.IOException: Server returned HTTP response code: 500 for URL:

Ho creato un java project e ho utilizzato questo codice:

package restfull;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Serializable;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSession;
/**
 * Main.java
 *
 * @author [url]www.javadb.com[/url]
 */
public class Main implements Serializable{

    /**
     *
     */
    private static final long serialVersionUID = 1L;

    /**
     * Extends the size of an array.
     */
    public void sendPostRequest() {

        //Build parameter string
        String data = "nome=pluto&cognome=pippo";
        try {

            // Send the request
            URL url = new URL("https://ip");
            //URLConnection conn = url.openConnection();
            //HttpsURLConnection.setDefaultHostnameVerifier ( new NullHostnameVerifier ()) ;
            HttpsURLConnection conn = ( HttpsURLConnection ) url.openConnection () ;

            conn.setDoOutput(true);
            conn.setRequestProperty("Accept-Charset", "UTF-8");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + "UTF-8");


            conn.setHostnameVerifier ( new NullHostnameVerifier ()) ;
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setRequestProperty("Content-Type", "text/plain");
            OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());


            //write parameters
            writer.write(data);
            writer.flush();

            // Get the response
            StringBuffer answer = new StringBuffer();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                answer.append(line);
            }
            writer.close();
            reader.close();

            //Output the response
            System.out.println(answer.toString());

        } catch (MalformedURLException ex) {
            ex.printStackTrace();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    /**
     * Starts the program
     *
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        new Main().sendPostRequest();
    }

    private static class NullHostnameVerifier implements HostnameVerifier {
        public boolean verify ( String hostname, SSLSession session ) {
            return true ;
        }
   }
} 

grazie mille.